Editing Staining (section)

=== Gram ===
{{main|Gram staining}}
[[Gram staining]] is used to determine gram status to classifying bacteria broadly based on the composition of their [[cell wall]]. Gram staining uses [[Gentian violet|crystal violet]] to stain cell walls, [[iodine]] (as a mordant), and a [[fuchsin]] or [[safranin]] counterstain to (mark all bacteria). Gram status, helps divide specimens of bacteria into two groups, generally representative of their underlying phylogeny. This characteristic, in combination with other techniques makes it a useful tool in clinical microbiology laboratories, where it can be important in early selection of appropriate [[antibiotic]]s.<ref>{{Cite journal|last1=Stone|first1=Rebecca B.|last2=Steele|first2=John C. H.|date=2009-07-01|title=Impact of Reporting Gram Stain Results From Blood Cultures on the Selection of Antimicrobial Agents|journal=American Journal of Clinical Pathology|language=en|volume=132|issue=1|pages=5–6|doi=10.1309/AJCP9RUV0YGLBVHA|pmid=19864226|issn=0002-9173|doi-access=free}}</ref>

<!-- Since this is a summary article, the following paragraph is probably more appropriate for the main article. Also, this explanation is one of two main theories. I think neither has been empirically demonstrated to date (see https://academic.oup.com/ajcp/article/132/1/5/1765499). -->On most Gram-stained preparations, [[Gram-negative]] organisms appear red or pink due to their counterstain. Due to the presence of higher lipid content, after alcohol-treatment, the porosity of the cell wall increases, hence the CVI complex (crystal violet – iodine) can pass through. Thus, the primary stain is not retained. In addition, in contrast to most Gram-positive bacteria, Gram-negative bacteria have only a few layers of peptidoglycan and a secondary cell membrane made primarily of lipopolysaccharide.